The present invention relates to a new and improved construction of a magnetic triggering apparatus or magnetic trigger for a selectively operative switch.
In its more specific aspects, the present invention relates to a new and improved construction of a magnetic triggering apparatus for a selectively operative switch, containing a plunger-type armature which is actuated by means of a magnetic coil or winding when there is flowing therethrough a current at least corresponding to a predetermined threshold or tripping current at which the contacts of the switch open. The plunger of the plunger-type armature acts upon a movable contact of the switch.
A magnetic triggering apparatus of such type is known, for example, from German Patent Publication No. 2,854,568. This publication also refers to the places of application, tasks and modes of operation of selective protective devices. With respect to the specifically described magnetic triggering apparatus, a plunger-type armature is actuated by means of a magnetic coil or winding when supplied with a current exceeding a predetermined threshold or tripping current. An extension of the plunger-type armature acts upon a movable contact and can open this movable contact. When the current decreases, the plunger-type armature is returned into its rest or inoperative position by the force of a spring. During such return movement, the plunger-type armature impacts upon a further extension which transmits this movement to a spring-loaded lever arrangement. A spring-loaded rod is rotatably attached to this lever arrangement and thus is swivelled in front of the extension of the plunger-type armature. When now a second current half cycle flows through the magnetic coil or winding during the residence or dwell time of the rod in front of the extension of the plunger-type armature, the extension of the plunger-type armature impacts upon the rod which, in turn, triggers the switch lock mechanism.
A further, selectively operative trigger is known from German Patent Publication No. 3,347,121 and U.S. Pat. No. 4,599,590, granted July 8, 1986. Therein, a U-shaped, spring-loaded lever arrangement embraces the magnetic trigger. When the striking or impact armature is first actuated, the plunger of the striking or impact armature impacts upon the lever arrangement. When the spring-loaded striking or impact armature recoils, a rearwardly-located extension moves the lever arrangement out of the effective range of the plunger, which can trigger a switch lock mechanism during a subsequent second current half cycle. It is a disadvantage of this type of magnetic trigger that the contacts for limiting the current are not opened by means of the striking or impact armature.
Furthermore, a magnetic trigger of an automatic switch such as known, for example, from German Patent Publication No. 2,115,030 contains a plunger-type armature which directly acts upon the movable contacts. A pivotable armature is arranged at the magnet yoke and, in its rest or inoperative position, supports the ratchet lever of the switch lock mechanism. When a tripping current flows through the coil of the magnet system, the pivotable armature is first attracted and releases the ratchet lever of the switch lock mechanism. As a result of the reduced air gap due to the attracted pivotable armature, the magnetic field is increased or strengthened such that the plunger-type armature is also pulled into the coil and the contacts open. Such a magnetic trigger is not suitable for selective switch triggering.